I am puzzled at your premise. It seems to me the words do mean what their nouns suggest.

Taking them in turn - and without thoroughly checking the etymology:
Bread has a range of meanings from food generally to a "baked and leavened loaf" to morsels of food.

Shortbread - is the easiest to comprehend. Shortening is fat in baking (probably most commonly noted in shortcrust pastry) so short bread being flour, sugar and fat easily becomes a shortbread.

Sweetbread - the bread here is probably more the morsels, and the principal sweetbread is the thymus - which, as you might know, tastes distinctly sweet compared to the savoury flavour of meat. For comparison my grandmother called tongue "throat bread".

I remember taking some parsnips to the south of France. The locals tried them and declared them "white carrots". So when coming across a small creature with a large head, no tail and grunts like a pig, it is unsurprising that it should be called a pig. A somewhat more successful comparison than the naming of the hippopotamus (a river horse). The Guinea is considered more an equivalent of "the mysterious east". Being of a pragmatic nature, I wonder if it was a deliberate ploy to mis-direct adventurers from finding more.

As for the word you are looking for I will continue to think about it.

P.S. where are you from? It just adds a bit of interest and understanding.

On your guinea pig theme Tony, I understand that penguins are so named because they resembled a species of bird that had become extinct in the Northern Hemisphere. Which is why birds with black heads are called "penguin" which is a corruption of the Welsh 'pen gwyn' which in turn means 'white head'.
Naturally, this just might be urban myth.

Last edited by Bobinwales on Sun Nov 18, 2018 10:55 pm, edited 1 time in total.

On your guinea pig theme Tony, I understand that penguins are so named because they resembled a species of bird that gad become extinct in the Northern Hemisphere. Which is why birds with black heads are called "penguin" which is a corruption of the Welsh 'pen gwyn' which in turn means 'white head'.

Is this like the jokey habit among Cockneys of calling someone who is around 78 inches tall 'Titch'?

I can't think of anything specific for such words, although, as Tony has pointed out, some have perfectly plausible etymology, such as "pineapple".

There are words that mean the opposite of what they mean (yes, this does make sense), and these are called "auto-antonyms" (such as "fast", which can mean "fixed" or "moving quickly"). But this is not what you are after.

Then there are things like "exocentric compounds", where part of a compound does not correctly refer to the other part (a redhead, for instance, has red hair, not a red head, unlike me in the current weather - I am nearly bald and have a red head, but I am not a redhead, neither, indeed, am I a redneck, although I have one ...).

But, again, this is not what you are looking for.

Examples such as the ones I gave for exocentric compounds, along with things like the "bread" of "sweetbread" and both the "pine" and "apple" of "pineapple" can all be seen as metonomy, as can the "Guinea", and possibly the "pig" of "Guinea pig", but that is still not a word to describe the precise phenomenon you refer to.

According to Wikipedia, which we all know is completely infallible, "The term "urban legend," as used by folklorists, has appeared in print since at least 1968. Jan Harold Brunvand, professor of English at the University of Utah, introduced the term to the general public in a series of popular books published beginning in 1981.

Jerusalem artichokes are not artichokes, and have nothing to do with Jerusalem.

An anecdote:
At school my French was pretty appalling, a dunce with a double hat. So when I had the temerity to challenge my French teacher on his translation of topinambour to artichoke , to great amusement of my form mates, I found my bottom warmed in the way that was traditional for boys in those days. A few days later a letter arrived for my French teacher from my father, on the letterhead of the Elysee Palace, it stated quite clearly and politely that the topinamour is a Jerusalem Artichoke and Artichoke translates as Artichoke (French spellings E&OE). I originally learnt of the arrival of the letter from the son of another master. And then again from the French Master as he attempted to beat French words into me as the letter from father had clearly indicated that my failure to master French was wilfull and an attempt to discredit his teaching.
C'est la vie.

I would like to think that your teacher was fired as a consequence of his cruelty and arrogance; but since that isn't how your anecdote ended, Tony, I assume that that didn't happen.

Nothing happened. I considered it at the time with little more than bemusement. The idea that it was cruel or inhumane just seems laughable. The lesson was learned: it is an art to find an appropriate way to correct a misunderstanding of a person inauthority. That was a lesson I learned well and has served me well in business.